1. Field of the Invention
The present invention relates to what is called a front-opening interface mechanical standard (FIMS) system, that is, a purge device to be used in a load port apparatus, for purging an interior of a pod, and the load port apparatus including the purge device, which is used for transferring, from one semiconductor processing apparatus to another semiconductor processing apparatus, wafers held in a sealed-type transport container called the pod, or for transferring the wafers from the semiconductor processing apparatus to the pod, during a semiconductor manufacturing process and the like.
2. Description of the Related Art
In recent years, in a general semiconductor manufacturing process, cleanliness is managed throughout the entire process by maintaining a highly clean state in only the following three spaces: inner spaces of various processing apparatus; an inner space of a pod capable of containing wafers and transporting the wafers from one processing apparatus to another processing apparatus; and a mini-environment in which the wafers are exchanged between the pod and the respective processing apparatus. Such a pod includes a main-unit portion which contains wafers therein and which has a wafer-insertion-and-removal opening formed in one side surface, and a lid which makes the inside of the pod serve as a sealed space by closing the opening. Further, a structure that defines the mini-environment includes an opening portion capable of facing the above-mentioned opening of the pod and a second opening portion arranged on the semiconductor processing apparatus side so as to face the opening portion.
The load port apparatus includes a member as a partition wall provided with the opening portion, that is, a wall called a side base, a door for closing the opening portion, a door drive mechanism for controlling operation of the door, and a mount table on which the pod is to be mounted. A mount base is capable of supporting the pod in such a manner as to face the opening of the pod and the opening portion each other, and brings the lid of the pod close to or apart from the door together with the pod itself. The door is capable of holding the lid of the pod. The door drive mechanism causes the door to open and close the opening portion under a state of holding the lid, and the door is caused to retract below a space between the opening portion and the second opening portion or to enter the space. A robot is arranged in the mini-environment, and the robot is capable of entering and retracting into/from the inside of the pod through the opening portion and the opening of the pod, and transfers wafers between the inside of the pod and the semiconductor processing apparatus also through the second opening portion.
In the semiconductor manufacturing process, the wafers contained in the pod may have, for example, metal wiring formed thereon. Such metal wiring has a risk that, due to surface oxidation thereof, desired characteristics cannot be obtained when a device is completed. Therefore, oxygen concentration in the pod needs to be maintained at a low level. As a technology provided to meet such a demand, Japanese Patent Application Laid-Open No. 2007-180517 discloses a configuration for maintaining the oxygen concentration in the pod at a low level by generating, when the wafers are inserted and removed into/from the pod, a gas curtain from an inert gas in parallel to the opening of the pod so as to suppress entrance of an oxidizing gas of the mini-environment into the pod, and by supplying the inert gas directly into the pod. Further, International Publication No. WO2005/124853 discloses a configuration for reducing the oxygen concentration in the pod by generating a space containing an inert gas at high concentration in the periphery of the opening portion of the pod, and in this state, supplying the inert gas into the pod.
In the above-mentioned mini-environment, entrance of an external atmosphere including dust or the like is prevented by, for example, supplying a clean air with use of a fan provided at an upper portion of the mini-environment so as to set a pressure slightly higher than an atmospheric pressure in the periphery. Further, processed wafers may have a gas, dust, or the like adhered thereto in the processing apparatus, and it is therefore necessary to prevent diffusion of the gas from the pod containing the wafers into the mini-environment. In view of this, in order to prevent the undesired diffusion of a gas, dust, or the like, it is necessary to provide a minute pressure difference so that the pressure level is set in an ascending order of the peripheral space, the interior of the pod, and the mini-environment.
In this case, in the configuration disclosed in Japanese Patent Application Laid-Open No. 2007-180517 or International Publication No. WO2005/124853, inert gas supply lines are separately provided so as to supply the inert gas into the pod and to the nozzles used for forming a high-concentration region of the inert gas or the gas curtain of the inert gas at the opening portion of the pod. Further, those inert gas supply lines are independently constructed also of the fan provided at the upper portion of the mini-environment. Therefore, in order to generate the above-mentioned appropriate pressure difference, supply amounts of the inert gas through the respective supply lines need to be controlled in parallel to control of the fan. The balance of the supply amounts is not easily adjusted, and further, in a case where the pod is upsized along with the upsizing of the wafers, the adjustment needs to be performed with extreme caution.